William Hague speaking in the House of Commons. Credit: PA/PA Wire/Press Association Images

British firms probably supplied the chemicals that have been used to make the nerve agent sarin in Syria, according to Foreign Secretary William Hague.

In a written statement to MPs he said that between 1983 and 1986 a review of the records showed a number of companies exported substances but they had legitimate uses for producing plastics and pharmaceuticals and they were not restricted under UK or international law.

He added: "From the information we hold, we judge it likely that these chemical exports by UK companies were subsequently used by Syria in their programmes to produce nerve agents, including sarin.Some of the companies involved no longer exist."

A UK chemical trader may have sourced some of the substances in question rather than producing them in the UK, he wrote.

Hague said Britain was "playing its full part" in the international effort to eliminate Syria's programme and he expected a ship carrying chemicals to be destroyed will arrive from the country next week.

David Cameron has said it's important he doesn't "pick Iraq's leaders" during a meeting with Nato's General Secretary Anders Fogh Rasmussen at Downing Street.

David Cameron speaks out about Iraq from Downing Street. Credit: ITV News

Mr Cameron told waiting journalists: "It's important that I don't pick Iraq's leaders, the people of Iraq pick their leaders, but what matters is that those leaders run that country on a non-sectarian basis, because running it on a more sectarian basis is part of the problem we are facing today."

The meeting took place as president Barack Obama prepared to announce that he is deploying about 100 Green Berets to Iraq to help train and advise Iraqi forces.